Bath or shower: which do you prefer?
WHICH DO U.S. TEENS PREFER?
Take a class vote. Survey people at your school. But don't stop there. Try different schools. Different age groups. What else? Write and let us know what you find out. (Be sure to tell us how you did your survey and include a copy.) Our address:
Science World Scholastic Inc. 730 Broadway New York, NY 10003
When you think of washing, you probably think of scrubbing away dirt and grime. But with each rinse, you also say good-bye to millions of dead skin cells (above) and bacteria (below). In fact, these bacteria may be the main reason you feel "dirty" after a workout. They cover your skin five million to the square centimeter, feeding off your body's oils and sweat. And they, not you, produce waste products that give sweat its characteristic stink. Washing removes these critters only temporarily. But fear not: They cause you no harm. Might their presence be doing you some good? What's your theory?
WHICH GETS YOU CLEANER?
What do you classmates think? Take a vote. Then do this experiment to find out who guesssed right. You'll measure cleanliness by sampling the bacteria and other microbes on your hands. The cleaning technique that leaves fewer microbes will be the winner.
WHAT YOU NEED:
* a sink with drain stopper and spray nozzle * soap
* magnifying glass * 3 petri dishes with nutrient agar
WHAT TO DO:
1. Start with clean hands. Then run them over your face, along countertops, floors, rugs, garbage pails and so on to coat them with oil, dust, and plenty of bacteria. (You may not see any of this "dirt.")
2. Uncover one of the petri dishes and touch the agar gel with the fingertips of one hand. Immediately replace cover and label the dish "Dirty--control." Note how your hands look and feel in the Data Table.
3. Now fill the sink with warm water and bathe your hands with soap under the water for 30 seconds. Swirl hands under water for 30 seconds to rinse. Shake off excess water. (Don't use a towel; towels are loaded with bacteria!)
4. Repeat Step 2 using the second petri dish. Label this dish "Bath."
5. Dirty hands exactly as before.
6. Have a friend hold the spray nozzle while you wash using the same water temperature, soap, and timing as before. (Rinse for 30 seconds under the spray.)
7. Repeat Step 2 using the third petri dish. Label this dish "Shower."
8. Place all three petri dishes agar side up on a cool shelf away from sunlight. Check them daily for one week (but don't uncover) to see if they show any differences in microorganism growth. Record your observations in the Data Table.
(Before discarding petri dishes, soak overnight in a mix of 1 cup bleach and 9 cups water.)
DON'T STOP NOW!
Would you recommend showers or baths to clean-conscious friends?
Would you get the same results using greasy dirt, like motor oil or hamburger grease? What about the effect of different soaps? Water temperatures? Try it.
WHICH USES MORE WATER?
The year is 2012. We Earthlings have wasted so much water that now we can only bathe once a week. Phewwwwy!
If you want a future that smells sweet, better start conserving now. Start by finding the least wasteful way to get clean. Is it in the tub or under the spray?
1. To find out how much water you would use in a bath: Measure the length and width of the tub and the height to which you would fill it with water. Multiply these numbers to get the volume.
2. To find out how much water you'd use in a shower. Run the shower for one minute, collecting the water in the tub or a large bucket. (Don't forget the water pouring out of the tap if your shower isn't 100 percent efficient.)
Measure the volume of water collected.
Now multiply that volume by the number of minutes you typically spend in the shower.
Which method used more water? (Use the collected water to wash dishes or water plants.)
DON'T STOP NOW!
Compare your results with others in your class and calculate a class average. Which method comes out on top now? Do you notice any differences between girls and boys? What factors might explain any differences? Using your survey results and the results from this activity, create a campaign to encourage water-conservation among teens.
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|Title Annotation:||includes related articles|
|Date:||Feb 12, 1993|
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